He does hide it. In the part in the graveyard where he is talking to Snape while they are poisoning Riddle Sr’s grave, he keeps spinning around, despite the fact that the eye lets him see 360 degrees regardless of where it is pointing.
If he’s escorting Potter around, everyone KNOWS he’d be on high alert, so they expect to see the thing whizzing around. Then they expect that when it isn’t whizzing around, it means he can’t see behind him.
And when they try to exploit that, that’s how he catches them.
It’s somewhat like the reason the Dark Mark isn’t always invisible. People will look for a weakness to exploit, so before they find one you should provide them with a fake one.
(If the Dark Mark were invisible and Moody wore an eyepatch, you’d just look for a different avenue of attack.)
He does hide it. In the part in the graveyard where he is talking to Snape while they are poisoning Riddle Sr’s grave, he keeps spinning around, despite the fact that the eye lets him see 360 degrees regardless of where it is pointing.
If he’s escorting Potter around, everyone KNOWS he’d be on high alert, so they expect to see the thing whizzing around. Then they expect that when it isn’t whizzing around, it means he can’t see behind him.
And when they try to exploit that, that’s how he catches them.
It’s somewhat like the reason the Dark Mark isn’t always invisible. People will look for a weakness to exploit, so before they find one you should provide them with a fake one.
(If the Dark Mark were invisible and Moody wore an eyepatch, you’d just look for a different avenue of attack.)